Trench isolation structure

Abstract

A trench isolation structure and method of forming the trench isolation structure are disclosed. The method includes forming a shallow trench isolation (STI) structure having an overhang and forming a gate stack. The method further includes forming source and drain recesses adjacent to the STI structure and the gate stack. The source and drain recesses are separated from the STI structure by substrate material. The method further includes forming epitaxial source and drain regions associated with the gate stack by filling the source and drain recesses with stressor material.

What is claimed: 
     
       1. A method comprising:
 forming a shallow trench isolation (STI) structure having an overhang which comprises forming a shallow recess of a first dimension in a substrate material followed by a trench of a second dimension formed in the substrate material; 
 forming a gate stack; 
 forming source and drain recesses adjacent to the STI structure and the gate stack, wherein the source and drain recesses are separated from the STI structure by the substrate material under the overhang; and 
 forming epitaxial source and drain regions associated with the gate stack by filling the source and drain recesses with stressor material such that the stressor material is formed under the overhang and stressor material under the overhang is separated from the STI structure by the substrate material. 
 
     
     
       2. The method of  claim 1 , wherein forming the overhang Comprises
 forming sidewall spacers within the shallow recess. 
 
     
     
       3. The method of  claim 2 , wherein the shallow recess is formed to a depth about 10 nm within the substrate. 
     
     
       4. The method of  claim 2 , further comprising removing upper portions of the sidewall spacers. 
     
     
       5. The method of  claim 2 , wherein the sidewall spacers are insulator material. 
     
     
       6. The method of  claim 2 , wherein forming the shallow recess comprising:
 implanting a dopant into an exposed portion of a substrate, through an opening in layers above the substrate; 
 annealing the substrate; and 
 selectively etching the substrate using a chlorine chemistry. 
 
     
     
       7. The method of  claim 6 , wherein the annealing is about 900 ° C. to about 1100 ° C. 
     
     
       8. The method of  claim 7 , wherein the dopant is an N-type dopant comprising one of phosphorus, arsenic, and antimony. 
     
     
       9. The method of  claim 1 , wherein forming the source and drain recesses includes forming facets along a side of the STI structure, bounded by the substrate material. 
     
     
       10. The method of  claim 9 , wherein forming the epitaxial source and drain regions comprises growing SiGe or SiC within the source and drain recesses, where the substrate material acts as a seed layer for the growing of the SiGe or SiC. 
     
     
       11. The method of  claim 1 , wherein the overhang is formed as a raised overhang portion. 
     
     
       12. A method, comprising:
 forming an opening in one or more layers formed on a substrate; 
 forming a recess within the substrate, in alignment with the opening; 
 forming an insulator liner on sidewalls of the recess; 
 forming sidewall spacers on the insulator liner with portions of the recess and opening; 
 forming a trench within the substrate, in alignment with the recess; 
 filling the trench and unfilled portions of the recess with an insulator material to form a shallow trench isolation (STI) structure; 
 removing the one or more layers and an upper portion of the sidewall spacers to form an overhang of the STI structure; 
 forming faceted source and drain recesses adjacent to the STI structure and under the overhang, which is bounded by portions of the substrate under the overhang; and 
 filling the faceted source and drain recesses with stressor material to form epitaxial source and drain regions such that the stressor material is separated from the STI structure under the overhang and the substrate acts as a seed layer for epitaxial growth of the stressor material at an interface of the faceted source and drain recesses at least under the overhang. 
 
     
     
       13. The method of  claim 12 , wherein forming the recess comprises:
 implanting an N-type dopant into an exposed portion of the substrate, through the opening; 
 annealing the substrate; and 
 selectively etching the substrate using a chlorine chemistry. 
 
     
     
       14. The method of  claim 13 , wherein:
 the annealing is about 900 ° C. to about 1100 ° C.; and 
 the N-type dopant is phosphorus, arsenic, or antimony. 
 
     
     
       15. The method of  claim 12 , wherein forming the source and drain recesses includes forming facets along a side of the STI structure, bounded by substrate material. 
     
     
       16. The method of  claim 15 , wherein forming the epitaxial source and drain regions includes growing SiGe or SiC within the recesses, where the substrate material bounding the source and drain recesses acts as a seed layer for growing of the SiGe or SiC. 
     
     
       17. The method of  claim 12 , wherein the overhang is formed as a raised overhang portion. 
     
     
       18. The method of  claim 12 , wherein the recess is formed to a depth about 10 nm within the substrate. 
     
     
       19. The method of  claim 1 , wherein:
 forming the source and drain recesses comprises forming faceted source and drain recesses using a sigma etch such that facets of the faceted source and drain recesses are provided under the overhang and separated from the overhang by the substrate material; 
 filling the faceted source and drain recesses with stressor material which is epitaxially grown using the substrate material at an interface of the faceted source and drain recesses at least under the overhang as a seed layer for the growth process; and 
 the stressor material is formed separated from the STI structure under the overhang. 
 
     
     
       20. The method of  claim 19 , further comprising forming an insulator liner on sidewalls of the shallow recesses, which is formed by an oxide growth process on the substrate material. 
     
     
       21. The method of  claim 20 , further comprising forming a spacer material on the insulator liner, the spacer material defining the second dimension of the trench. 
     
     
       22. The method of  claim 21 , wherein the overhang is formed as a raised overhang portion by selective removing the substrate material on sides of the shallow recess. 
     
     
       23. The method of  claim 21 , wherein the spacer material is larger in thickness than gate sidewall spacers.